1. Field of the Invention
The present invention relates to a plasma arc torch and, more particularly, to a cooling device and system for a plasma arc torch and associated method.
2. Description of Related Art
Certain welding and cutting equipment, including plasma arc torches and associated equipment, often require significant electrical power supplies for effective operation. Such power supplies may include one or more power modules that generate the power required for torch operation. For example, the power modules may be required to collectively provide from about 1-120 kilowatts (kW) or more of power for a torch. These power modules may be, for instance, IGBTs, SCRs or other suitable power modules. One example of a typical power module 50 is shown in FIG. 1. In generating the power for the torch, such power modules also generate a significant amount of heat. As such, one surface of the power module, such as the bottom surface, may be configured to be flat and smooth so as to allow the surface to engage a heat sink device for removing excess heat from the power module. In some instances, the heat sink device is a metal component provided with multiple fins to increase surface area of the heat sink device and thereby enhance convection of the heat away from the heat sink device. In further cases, the heat sink device may be subjected to a stream of air blown across the fins to further enhance convection of the heat. In this manner, the goal is to limit the temperature of the power module during torch operation to an acceptable level.
In some instances, the heat sink device may comprise a discrete and closed liquid cooling plate as shown, for example, in FIG. 1. The cooling plate 10 includes a fluid circuit 15 for a liquid coolant encased within, for example, a metallic heat-conducting element 20 generally forming the overall structure of the cooling plate 10. The self-contained cooling plate 10 is engaged with a surface, such as the bottom surface, of the power module 50 to provide cooling therefor. Such a cooling plate 10 may also implement its own circulating cooling system (separate from the cooling system used to cool the torch head) including, for instance, a pump and a heat exchanger, for circulating a cooling fluid through the fluid circuit 15 to provide a medium for removing heat from the power module 50. However, in such a configuration, the heat from the power module 50 must pass through the material of the heat conducting element 20, as well as the material of the fluid circuit 15, before reaching the liquid coolant. In some instances, an interface material such as a gasket or thermal grease may be disposed between the heat-conducting element 20 and the power module 50 (as well as between the heat sink device and the power module in the above-described air-cooled heat sink), which may further increase the components through which the conducted heat must pass in order to reach the cooling fluid. As such, these thermal conduction issues may limit the cooling efficiency of the cooling plate 10 in this application.
In any instance, the separate configurations (air-cooled heat sink or separate cooling plate) for cooling the power module(s) may tend to be inefficient or insufficient mechanisms for removing heat from the power module. Inefficient or insufficient removal of heat from the power module may cause a reduction in the power output thereof. In such cases, a larger power module, or additional power modules, may be required to provide sufficient power for operating the torch. In addition, the separate provisions (air-cooled heat sink or separate cooling plate) for cooling the power module(s) may, in some instances, result a bulkier or larger power supply for the torch (due to the extra components), a costlier power supply (and costlier system overall), possibly a less reliable power supply, or a more complex power supply.
Thus, there exists a need for a simpler and more efficient cooling system for the power module(s) of a power supply, wherein such a cooling system may also desirably provide increased reliability, less cost, and a smaller or less bulky power supply for the torch.